Too tired for a huge-ass post, so you get an edit and an explanation.
Yours has a cuter air to it, I kinda like it, but in case you want a different direction.
First, and most important to this, the back leg. On such a condensed sprite, having that shape of leg just won't do DK justice, despite the realism. Also, something that helps the balance: DK has ape feet. Literally. His feet are goddamn huge. You can also pull the back leg back a pixel to help sell the hunch.
The next two things are a bit iffy in my mind. The first was lowering the head a pixel. This definitely sells the hunch better, but it obscures, and changes the height from that of the front sprites. Speaking of the head, the facial expression(read "eyes") totally have that DK attitude in them.
The other iffy thing was to reach his arm forward a bit more. Every time I think about my doing this, I think it less and less a good idea. Maybe it's 'cuz I can't fix up the shading like you did it. You be the judge.
Drop the back arm. Your other side views are perfectly horizontal, so match conventions.
Something I am adamant about though, is the hands. I recommend showing the hand right on from the side, with the curled up fingers that he's lunging about on. I didn't do it very well right now, but I hope the edit got the point across.
Also, plant the feet and hands SOLID. look at M&L's feet on the side views. They land flush on the ground. DK's are curling up a bit. I just realized I missed a pixel at the back of DK's back foot btw, make the foot totally flush with the ground. On much of the hand, do the same, but let it curl up at the curling fingers, because they actually are gradually raising off the ground.
Oh, and touch some highlight on his head tuft.
Good luck, and good night.